During the coking of coal, normally 140 l of coal water per ton of coal can result, approximately 100 l thereof coming from the initial moisture content of the coal and approximately 40 l resulting from the coking process itself. During coking, in addition to the volatile noxious substances like NH.sub.3, H.sub.2 S and HCN, fixed salts, mainly NH.sub.4 Cl can be produced, can be dissolved in the gas condensate, and cannot be removed again by desorptive processes. Therefore, up to now it has not been possible to reuse as service water the gas condensate resulting from such cleaning steps as dephenolizing or stripping in the still, because its salt content remains high even after the release of the fixed ammonia with lime or alkali.
Normally, in a coking plant, the hot gas at about 800.degree. C. coming from the rising main is cooled in the condenser down to the dew point of about 80.degree. C. by the gas condensates guided in closed circuit. Thus only a part of the fixed salts reach the closed-circuit condensate partially; the rest goes together with the gas into the cooler condensate, so that the separation of the gas condensate into a salt-containing and a salt-free fraction cannot take place.
However, a process for the production from a condensate free of fixed salts is known, wherein the crude gas is scrubbed between the condenser and the primary cooler, in order to eliminate the fixed salts from the gas (U.S. Pat. No. 1,747,616). An examination of this process dating from the year 1922 shows that this process has not been a success, because the fixed salts are present in the form of aerosols, which can not be eliminated through scrubbing.